The objective of this work is to investigate the structural and biochemical state of the cytoskeletal protein actin on the red cell membrane. Further, we propose to lay the foundations for studies of the diseases hereditary sphero and eliptocytosis (which may be the result of cytoskeletal abnormalities) and also for studies of cytoskeletal-membrane associations in complex blood cells, such as monocytes, platelets and macrophages. Our experiments focus on defining the role of the cell membrane as a catalytic structure which may influence or promote associations of actin with itself or with other membrane or cytoplasmic proteins. We hope to identify the membrane components (likely to be proteins) which are responsible for the association of actin with the red cell membrane and will examine the structure of actin complexes with purified membrane proteins in solution to obtain information on the kinds of associations to be expected on the membrane.